ZCZC SPCSWOMCD ALL
ACUS11 KWNS 162323 
SPC MCD 162323 
MNZ000-IAZ000-SDZ000-170100-

Mesoscale Discussion 1761
NWS Storm Prediction Center Norman OK
0623 PM CDT Thu Sep 16 2021

Areas affected...Eastern South Dakota...Southwest and Central
Minnesota...Far Northwest Iowa

Concerning...Severe potential...Watch likely 

Valid 162323Z - 170100Z

Probability of Watch Issuance...80 percent

SUMMARY...A severe threat is expected to develop from central
Minnesota southwestward into far southeastern South Dakota. Large
hail and wind damage will be the primary threats. Weather watch
issuance will likely be needed across the region early this evening.

DISCUSSION...Latest surface analysis shows a cold front moving
southeastward across west-central Minnesota and southeastern South
Dakota. A moist airmass is located ahead of the front with surface
dewpoints generally in the lower to mid 60s F. This is contributing
to a narrow corridor of moderate instability where the RAP is
estimating MLCAPE in the 2000 to 2500 J/kg range. This combined with
increasing low-level convergence just ahead of the front will
support continued thunderstorm development this evening. In addition
to the instability, RAP forecast soundings early this evening across
southwest Minnesota have veering winds with height in the low levels
with about 50 kt of west-southwest flow at 500 mb. This is helping
to create 0-6 km shear near 40 kt, which will likely support severe
thunderstorm development over the next few hours as cells gradually
increase in coverage. Although supercells with large hail will be
possible, the stronger line segments may also be able to produce
wind damage as well.

..Broyles/Edwards.. 09/16/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MPX...FSD...ABR...

LAT...LON   43189516 42909573 42879646 42909712 43109732 43569737
            44239699 45569611 45939531 45889478 45659442 45059446
            44469479 43189516 

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